"Windows blocked the installation of a digitally unsigned driver" when installing Symantec Endpoint Protection Cloud (SEPC) from client redistributable, the Windows Installation package that is downloadable from the SEPC Security Cloud Portal web site.
A digitally signed driver is required
Symantec DC Control Driver
Windows blocked the installation of a digitally unsigned driver. Uninstall the program or device that uses the driver and check the publisher's website for a digitally signed version
of the driver.
This issue appears to occur when "Secure Boot" is enabled in UEFI BIOS.
The error does not actually block the installation. The error finishes and registers OK with the SEPC portal.
Upgrade to 18.104.22.168 of the SEPC client software.